This invention relates generally to the field of data storage and more specifically to a system and method for storing data in read-only memory.
The rising use of semiconductors in a variety of implementations has led to the increasing demand for more efficient storage of data. Semiconductors are used in a number of products, including computers, automobiles, and household appliances, and are often used to store an increasingly large amount of data in read-only memory (ROM). Moreover, as computational devices become smaller, the space available for storing data has decreased. Known methods for storing data, however, have not been satisfactory in terms of storage efficiency and ease of production.
Data is stored in ROM by encoding values using a pattern of connections on a semiconductor. Known approaches for programming connections include via, metal, gate, and moat programming. Via programming uses vias, couplings from one semiconductor layer to another, to establish connections. Although via programming is relatively easy to produce, it yields a low storage density, represented as the number of storage bits per unit area, compared to other known ROM programming techniques in similar semiconductor processes. Metal programming establishes connections using metal layers, and is also relatively easy to do. Metal programming, however, also yields a low storage density compared to other known ROM programming techniques. Gate programming uses transistors to establish connections. This type of programming allows for storage of relatively large amounts of data per unit area, but results in slow storage and retrieval. Moat programming uses moats formed in the substrate of the semiconductor to establish connection and also allows for the storage of a relatively large amount of data. In moat programming, however, the programation of the connections must be established during the earliest stages of semiconductor production. Since a ROM cannot be programmed until after a customer has submitted a programming request, programming a semiconductor in the earliest stages results in a relatively long period from customer request to delivery of the product.
While these approaches have provided improvements over prior approaches, the challenges in the field of data storage have continued to increase with demands for more and better techniques having greater storing efficiency and production. Therefore, a need has arisen for a new system and method for storing data in read-only memory.
In accordance with the present invention, a system and method for storing data in read-only memory are provided that substantially eliminate or reduce the disadvantages and problems associated with previously developed systems and methods.
According to one embodiment of the present invention a system for storing data in read-only memory is disclosed that comprises bit level conductors, transistors, and sets of reference level conductors. Each reference level conductor has a reference value. A selected reference level conductor transmits a selected reference value to one of the transistors. The transistor transmits the selected reference value to a selected bit level conductor having a selected bit value. The bit level conductors, the transistors and the reference level conductors store data by encoding data as a combination comprising the selected bit value and the selected reference value.
According to one embodiment of the present invention, a method for storing data in read-only memory is disclosed. Bit level conductors having bit values, transistors, and sets of reference level conductors having reference values are provided. A selected bit value of a selected bit level conductor and a selected reference value of a selected reference level conductor are selected. Data is encoded by translating the data from a digital form to a combination comprising the selected bit value and the selected reference value. The data is stored by coupling the selected bit level conductor to the selected reference level conductor such that the selected reference level conductor can transmit the selected reference value to the selected bit level conductor. The reference value may be transmitted to the bit conductor through a switch, for example, a transistor, in a semiconductor process.
A technical advantage of the present invention is that it uses up to all available or additional conduction layers, such as metal layers, of a semiconductor process to store data. The use of additional layers results in the storage of a large amount of information in a relatively small area. Another technical advantage of the present invention is that the programming of the semiconductor occurs in the later stages of production. By programming at later stages, the present invention allows for faster production of semiconductors from the time of the customer""s programming request. Consequently, the present invention allows for the fast production of semiconductors that are able to store a large amount of information.
Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.